In the westernmost province of the Country of Tokyo - a country that shares nothing in common with Tokyo as you may know it - there live two girls. Kasha, a small orange-haired catgirl, and Milchi, a giant amazon tiger girl.

They live in the former summer home of Milchi's parents - a home built directly into a small mountain, known as "Mellow Rock". They enjoy a happy life together filled with sunshine, food and fun. Although it seldom rains on their sun-drenched home, Milchi knows the true source of sunshine in her life is Kasha's smile, and does everything to ensure that it's always beaming. And Kasha may not be aware of it, but she unwittingly does the same thing for Milchi.